1. Field of the Invention
The present invention relates to an apparatus for transferring a motor vehicle in a multistory parking lot, wherein a motor vehicle is transferred from a carriage of a stacker crane to a containment rack.
2. Description of the Related Art
In a multistory parking lot having multistory containment racks, a motor vehicle transfer apparatus is used either to transfer a motor vehicle on a carriage of a stacker crane to a containment rack or to transfer a motor vehicle on a containment rack to a carriage. A conventional motor vehicle transfer apparatus transfers a motor vehicle as follows.
A motor vehicle having been transferred to an entrance of a multistory containment rack is placed on a pallet. The motor vehicle together with the pallet are put on a carriage by slide forks installed on a stacker crane. The carriage with the motor vehicle thereon is aligned with an empty containment rack by moving the stacker crane. The motor vehicle together with the pallet are transferred to the containment rack by operating the slide forks. When a motor vehicle on a containment rack is to be sent off, the motor vehicle together with a pallet are transferred from the containment rack to a carriage by operating slide forks of a stacker crane. Then, the motor vehicle is transferred to an exit by operating the stacker crane.
Japanese Patent Application Laid Open No. 141181/76 discloses a stacker crane for a multistory parking lot which transfers a motor vehicle directly between a carriage of a stacker crane and a containment rack. This prior art stacker crane has a structure as described below.
The carriage of the stacker crane of Japanese Patent Application Laid Open No. 141181/76 moves to-and-fro relative to the containment rack. A plurality of slide forks hold front and rear wheels of a motor vehicle. One of the plurality of slide forks is freely movable to expand and reduce a distance between the slide forks. A motor vehicle is placed on a slat conveyer installed at an entrance of a multistory parking lot by driving the motor vehicle and hand brakes are applied to the motor vehicle. The power supply of the slat conveyer is turned off. A position of the carriage of the stacker crane is aligned with a position of the motor vehicle. The slide forks are expanded toward the outside of the front and rear wheels of the motor vehicle. Then, one of the slide forks is moved in a longitudinal direction of the motor vehicle and in a direction wherein a distance between the slide forks is reduced. The front and rear wheels are held by the slide forks, the outside of the front and rear wheels being put between the slide forks.
On this occasion, one of the slide forks contacts the outside of the wheels. When the other slide fork does not contact the wheels, the motor vehicle is pushed by the slide fork having previously contacted the wheels. Since the power supply for the slat conveyer is off, the wheels can be put between the slide forks with the smallest force in a direction wherein the slat is pushed. The motor vehicle is put on the carriage by reducing the distance between the slide forks. Also, when the motor vehicle is transferred from the carriage to the containment rack or from the containment rack to the carriage, the transfer of the motor vehicle is carried out by operating the aforementioned slide forks.
In a method for transferring a motor vehicle on a pallet, an empty pallet is required to be returned to an entrance of a multistory parking lot after a motor vehicle is sent off from an exit of the multistory parking lot. Moreover, in preparation for generation of unbalance of the number of motor vehicles coming in and going out, pallet stockers for keeping pallets are necessary. When a difference between the number of motor vehicles coming in and the number of motor vehicles going out is increased, the capacity of the pallet stockers becomes insufficient. In consequence, pallets which cannot be contained in the pallet stockers are required to be contained in containment racks. Therefore, an additional space is required, and wasteful labor is spent for moving only the empty pallets, which gives rise to a high equipment cost and management cost.
The method of Japanese Patent Application Laid Open No. 141181/76 has an advantage in that no pallet is required. This method has a disadvantage, however, in that there are only a few holding points because front and rear wheels are held by putting only the outside of the front and rear wheels between slide forks, and therefore, a motor vehicle is liable to move to-and-fro during movement of a stacker crane, which makes the motor vehicle unstable. Particularly, in the case of a motor vehicle in which hand brakes are applied, since the wheels do not rotate when the wheels are put between the slide forks, slip or sliding between the slide forks and the wheels is produced, which leads to abrasion of the tires of the wheels.
In addition, when a motor vehicle contained in a containment rack is sent off, since there is no apparatus such as a slat conveyer for freely moving the motor vehicle, the tires of the wheels slip on the containment rack, which abrades the tires.